Problem: 3 folders cost $4.41. Which equation would help determine the cost of 6 folders?
Answer: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 3 folders. We want to know the cost of 6 folders. We can write the numbers of folders as a proportion: $\dfrac{3}{6}$ We know 3 folders costs $4.41. We can let $x$ represent the unknown cost of 6 folders. The proportion of these costs can be expressed as: $\dfrac{\$4.41}{x}$ The cost changes along with the number of folders purchased, and so the two proportions are equivalent. $\dfrac{3}{6} = \dfrac{\$4.41}{x}$